Coherence and anticoherence resonance in high-concentration erbium-doped fiber laser

Abstract

We report an experimental study of low-frequency (~10 kHz) self-pulsing of the output intensity in a highconcentration erbium-doped fiber laser. We suggest that the fast intensity fluctuations caused by multimode and polarization instabilities play the role of an external noise source, leading to low-frequency auto-oscillations through a coherence resonance scenario. © 2010 Optical Society of America OCIS codes: 060.3510, 060.2410, 140.3500, 140.1540 Output intensity self-pulsing in high-concentration erbium-doped fiber lasers (HC EDFLs) has been extensively studied for its importance in communications, reflectometry, distributed fiber-optic sensing, biomedicine, etc. [1][2][3][4][5][6][7]. For a long time, the presence of clustered erbium ions and their role as saturable absorber was regarded as the only possible mechanism responsible for self-pulsing at frequencies of 10-100 kHz [7]. However, detailed microscopic study of erbium-doped glasses by means of x-ray-absorption fine structure spectroscopy (XAFS) has revealed a short-range coordination order of erbium ions, rather than pair clustering [8]. It was also found that suppression of the short-range order leads to improved characteristics of high-concentration erbiumdoped fiber amplifiers and lasers. The suppression can be realized by increasing the solubility of erbium in the host matrix (codoping by Al [9]) or by changing the deposition process (direct nanoparticle deposition [10,11]). Because self-pulsing was observed in HC EDFLs even with these types of fibers, the pair-clusters approach cannot explain this effect [4,5]. On the other hand, experiments and theory indicate that the pump-tosignal intensity noise transfer (PSINT) can significantly contribute to low-frequency self-pulsing [4,5]. However, PSINT decreases as the pump current increases, and therefore this process can induce self-pulsing only near the lasing threshold [1,2]. To reveal a mechanism that can drive self-pulsing with pump currents beyond the lasing threshold, we test and experimentally prove the concept of coherence and anticoherence resonance (CR and ACR) [12][13][14]. The details are reported in this Letter. The experimental setup used to study self-pulsing in EDFL is shown in Fig. 1. The laser cavity consists of a high-concentration (c Er ¼ 3:7 10 25 ions=m 3 ) erbiumdoped fiber (5 m, Liekki Er40-4/125), with a Faraday mirror (R ¼ 90%) and a fiber Bragg grating (λ peak ¼ 1556 nm, Δλ 3 dB ¼ 0:2 nm, R ¼ 86%) as reflectors. According to manufacturing data [10] and previous experimental results [11], the short-range coordination order of erbium ions is suppressed and no saturable absorption is present. Total intracavity losses are 5 dB. The Faraday mirror rotates the plane of polarization of the reflected beam by π=2 at λ ¼ 1550 nm. To pump the erbium-doped fiber, we used a 978 nm laser diode (LD) with a tunable current source (200-600 mA). The pump current at the lasing and self-pulsing threshold was 240 mA.To characterize the polarization instability as a possible source of high-fre...

Vector solitons with locked and precessing states of polarization

“…As follows from Figs. 2-5, phase difference dynamics indicate the presence of coherent coupling between cross-polarized SOPs through the gain sharing and pump and in-cavity polarization controllers similar to the polarization dynamics of single-and multi-mode lasers without a saturable absorber [5][6][7][8][9][10]. It is well known from the theory of nonlinear coupled oscillators that weak coupling leads to a complex behavior, and increasing the coupling leads to stabilization of the behavior, i.e.…”

“…In such systems two laser modes with the same longitudinal and transverse spatial patterns and different polarization states, frequencies, and amplitudes interact through the gain sharing, phase-and amplitude selective nonlinear processes (Kerr nonlinearity) and in-cavity components (polarizers, polarization controllers etc.). As a result of the interaction, different polarization patterns have been found including polarization chaos [5][6][7][8][9][10]. In fiber lasers, due to long cavity length and wide gain bandwidth, typically, a large number of modes are generated.…”

“…In fiber lasers, due to long cavity length and wide gain bandwidth, typically, a large number of modes are generated. This leads to stochastic polarization dynamics as a result of spontaneous modelocking [9,10]. However, implementation of passive or active mode-locking techniques results in suppression of stochastic dynamics and so regular dynamics in the form of dissipative solitons were observed [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”

Event-triggered feedback in noise-driven phase oscillators

“…Interestingly, it also leads to an local maximum of the C v at a low noise level (D ≈ 0.02 − 0.03). Such a maximum indicates anti-coherence resonance (ACR) [57] or incoherence resonance [3] and has been observed in models as a consequence of either damped subthreshold oscillations [57], or due to a finite refractory period [47]; for an experimental verification, in a laser system, see [58].…”

Manipulating coherence resonance in a quantum dot semiconductor laser via electrical pumping

“…In contrast to stochastic resonance (see [37] for a review) the effect occurs without periodic forcing of the system. Coherence resonance is already an intensively studied effect and was shown theoretically in quantum well (QW) lasers with saturable absorber [28], in QD lasers under optical injection [38], in lasers subject to long optical feedback [32,39], in laser systems with polarization instabilities [40,41], in semiconductor superlattices [42], as well as in non-excitable systems below a subcritical Hopf-bifurcation [43][44][45].…”